In the future, even the trees will be keeping tabs on us. Seven years of government-funded research to develop alternate avenues of national defense have finally borne fruit in the form of "plant sentinels," color-changing, chemical-sniffing shrubbery created by Colorado State University biologist June Medford and her crack team of chemical researchers. According to a recent article in the Denver Post, the CSU team has modified common plants to change color in the presence of potentially hazardous chemicals like drugs, pollutants or even explosives.

Here's how it works: Medford and co. developed synthetic periplasmic binding proteins to create custom receptors in common plants like arabidopsis that chemically react to particles of toxic chemicals, hazardous pollutants, explosive material and other silent but deadly threats. The biologists then employed a bacterial solution to modify the genetic structure of sample plants and encourage growth of the chem-sniffing receptors; successful transplantation creates a plant that fades from green to white when it detects deadly chemicals in the air, water or soil.

U.S. military agencies like the Department of Defense and the Department of Homeland Security have been funding this project since 2003, and multiple military applications have already been suggested both at home and abroad, from revealing roadside bombs in foreign warzones to sniffing out smugglers at U.S. ports.In fact, genetically modified plant sentinels may soon be employed across the country to create a decentralized, automated explosive early-warning system.

We're not just talking about airports and border crossings either; as Homeland Security representative Doug Bauer told the Post, "our hope is if these plants could be located ubiquitously, we might be able to detect explosives at the point they are being assembled."

So what's keeping Homeland Security from sowing these sentinels on every street in America? For the moment, speed; Medford's plants take hours to complete the color change from green to white.

As it stands there's little use in drug-sniffing super-plants that take three hours to let you know someone's smoking something shady, but the Defense Department's Defense Threat Deduction Agency has provided $7.9 million for the express purpose of speeding up the chemical reaction that causes color change and getting plant sentinels out on the streets for real-world testing.

With luck, Medford's team will be sure to sterilize the genetically-modified chem sniffers to ensure the man-made plant sentinels don't accidentally overrun indigenous shrubbery across the country.